Dredges dig and remove material, such as sand and gravel, from the bottom of bodies of water, such as lakes and rivers. The primary means for dewatering dredged or slurried material is typically a vibrating screen unit having a deck surface covered by a screen mesh media which has a matrix of openings of a predetermined size and arrangement. Unlike conventional vibrating screen applications where material separation is achieved by having as much material as possible of a size less than that of the openings in the screen media fall through the screen deck surface, dewatering of material is achieved by retaining as much of the material less than the size of the openings as possible on the screen deck surface while passing the water through the openings. During dewatering, a small amount of fine grit passes through the openings in the screen mesh media while the dewatered material is discharged onto a conveyor belt for processing at a discharge end of the unit.
In general, for a particular feed material, the dewatering efficiency of vibrating screen units is dependent on the size or surface area of the screen deck. Capacity can be increased by enlarging the screen deck of vibrating screen units and increasing the feed rate of slurry. However, the economics of sizing up vibrating screen units to increase capacity can be significant and even cost prohibitive.
The present invention provides vibrating screen units which have increased dewatering efficiencies for given overall sizes.